When to follow up after AOS interview?

[punchy 1]

Hi all,

We had our interview on 28th of July. At the end of the interview Officer said she would recommend our application for approval. And gave us a paper saying " your application has been recommended for approval..." And she said I would receive the card in 2 weeks. And informed us about ROC as well. And then I told her that my work permit would be expired on 9th of September and I had a full time job and what to do if I didn't receive it. Then she said it wouldn't take that long and I would definitely receive it by then.

We left the office whith the idea that we would receive an update in of couple days.Because she was so clear about it.

Well it's been 2 weeks and no updates at all. Fortunately I had applied for EAD renewal and I received approval notice yesterday. For now it's not a big deal. At least I have my EAD. But just wanted to ask and to be prepared for the next;

1) If they are not able to send it in 2 weeks, why would they tell you they are? (I guess there is no answer for this...)

2) Why is it taking so long? Waiting for Supervisor's approval? Running extra security checks? ( Then why do they not state this on that paper notification they gave us? Like "your application needs to be reviewed / Pending security checks etc.)

3) When should I follow up with them? after 30 days? 120?

I know a lot of people are still waiting and this is the only rule of this game. But maybe there are some people have some answers.

Thank you.